Door operating mechanism



March 9, 1965 M. c. wlLsoN 3,172,651

DOOR OPERATING MECHANISM Filed Oct. l, 1962 3 Sheets-Sheet 1 f3 /l/ /l/l/l r l D l n lod" M. c. WILSON Dooa OPERATING MECHANISM March 9, 1965 3 Sheets-Sheet 2 Filed Oct. l, 1962 March 9, 1965 M. c. wlLsoN 3,172,651

DOOR OPERATING MECHANISM Filed Oct. l, 1962 3 Sheets-Sheet 3 INVENToR. MERUN C. \N\\ 5ON Mammml ATTORNEYS S P rc I Y '3,172,651 Unlted ytates atent Ice dem Mm, ,9, 65

mechanism from that illustrated in FIGURES land 2, 3,172,651 with the door being shown in open position;

DOOR IERATING MECHANISM -Merlin C; Wilson, P). Box '26211,*Derita'Statiom Charlotte, N.C.

Filed ct. 1,1962, Ser. N0.227,166 Claims. (Cl. 268-53) This invention relates to a new and improved mecha- V-nism for operating asliding door by remote control to move the door-between positions opening and closing a door opening in a building structure.

Heretofore, door operators for moving sliding doors havebeen characterized by their inclusion of rather complicated mechanical linkages. These mechanical linkages are either assembled for cooperation with a longitudinally extending rail or trackway provided by a component part wholly separate from the rail or trackway with which the door is associated for sliding movement while suspended therefrom, or may be disposed adjacent one boundary of the door opening to present an unattractive appearance. In the latter instance, the door operating mechanism is fully exposed to foreign matter and is likely to be rendered inefiicient or even inoperative because of the accumulation of such foreign matter on the various components thereof which alsocontributes to an unsightly appearance.

Accordingly, it is an object of this invention to provide an improved door operating mechanism for sliding doors which is of .simplified construction and comprises relatively few parts as compared to conventional door operating mechanisms with the parts being so arranged that the improved door operating mechanism is not likelyto become inoperative or to require frequent repairs.

It is another object of this invention to provide an improved door operating mechanism for sliding doors in which the components comprising the mechanical linkage system for moving the door between open and closed positions are confined within the same housing providing the longitudinally extending trackway from which the door is suspended for sliding movement.

Itis another object of this invention to provide an improved door operating mechanism utilizing a non-reversible motor as a source of power for moving the door between open and closed positions, wherein an endless loop is adapted to be driven in a single direction bythe non-reversible motor with the door being connected to the loop by a door operator means of simplified construction which is capable of imparting reciprocating movement to the door between open and closed positions eventhough the endless loop is limited to travel in a single direction.

Some of the objects of the invention having beenstated, other objects will appear as the description proceeds when taken in connection with the accompanying drawings, in which- FIGURE 1 is a fragmentary side elevational View of the improved door operating mechanism according to the present invention, showing the door in open position;

FIGURE 2 is a fragmentary side elevational View similar to FIGURE l, but showing the door in closed position;

FIGURE 3 is a top plan View of the door operating mechanism;

FIGURE 4 is an enlarged transverse sectional view taken along the line 4 4 in FIGURE 2;

FIGURE 5 is an enlarged transverse sectional View taken along the line 5 5 in FIGURE l;

FIGURE 6 in an enlarged fragmentary view, partially in side elevation and partially in longitudinal section, taken substantially along the line 6-5 in FIGURE 5 and looking at the opposite side of the door operating `of the slidable door '10 in a suitable manner.

Alel relationship therebetween. `idler sprocket mounted vfor rotation about a fixed axle Vor shaft I9 which extends transversely into the housing FIGURE 7 is an enlarged fragmentary view, partially in side elevation and partially in longitudinal section, similar to FIGUREy 6, but showingv the door at a position intermediate the open and closed positions thereof:

'FIGURE 8 isawiring diagram of the electrical system for controlling thedoor operating` mechanism;

FIGURE 9 is an enlarged fragmentary perspective view of the housingfrom which the door is suspended for sliding movement and in which the door operating mechanism is contained; and

FIGURE l0 is anenlarged `fragmentary perspective View of thetdoorpperating mechanismvasoperably :connected tothe -sliding doo'rfa4 pivotal operator link associated withfthe door andan endless chain being shown in full lines and phantom lines to indicate the two different positions assumed by the operatorlink in causing movementof the door in opposite directions.

Referring more specifically to the drawings, the door operating mechanism in accordance with the present iuvention is associated with a sliding door i0 of the type movable between open and closedl positions with respect toadooropening in a building structure, the door operatingmechanisrn being effective to accomplish such movement of the door 1t) automatically upon its actuation.

The door '10 is suspended from a longitudinally extending or elongated housing 11 by roller assemblies 12, A12.*which are -movable along a trackway or rail ,13 extending along the lower wall of the housing 11, the roller assemblies 12, I2 being mounted on the upper end edge It will be noted that the-housing 11 includes an upright mounting Vflange 114 above the top wall thereof through which .suitable fastener elements may .extend for aflixing the housing V11 to the building structure adjacent the door Y opening.

The door operating mechanism comprises a driven endless loop means in theform of a chain I5 disposed within the `housing 'II and extending lengthwise therein 4to provide substantially parallel upperand lower chain sections joined by arcuate chain portions at the opposite ends ofthe chain 15. The chain I5 is entrained about a pair of spaced pulleys, shown as sprockets 16, I7, which are carried within the housing 11 at opposite ends thereof by means to vbe presently described. An intermediate idler pulley, shown as sprocket 18, may be prolvided to support the intermediate portions of the upper and lower chainsections for maintaining a spaced paral- The sprocket 16 is an 11 at one end thereof, the fixed axle 19 being received by an enlarged hub 2@ formed on the sprocket 16.

As `best shown in FIGURES 4, 9, and l0, the end of `the `fixed axle .19 disposed outwardly of the housing 11 is supportedin the central web portion 22 of a U-shaped bracket member 21 aixed to the housing 11. The central webportion 22 of Ithe bracket member 21 vis laterally spaced from the adjacent side wall of the housing 11 by the legs '23, 23 of thebracket member 21, and the outer end ofthe fixed axle 19 is fastened in place by nuts 24,

2li threadably received thereon and engaging the opposite side surfaces of the central web portion 22 of the bracket member 21. The distance between the sprockets i6, 117 may be adjusted to compensate for wear of the chain 15 and for adjusting the effective 'length of the upper and lower chainsections to conform to the distance to be traveled by thedoor 10 in moving between open and .closed positions. In the Vlatter connection, it will be observed in FIGURES `9 and 10, that the central web portion 22 of the bracket member 21 and the adjacent side wall of the housing 11 laterally spaced therefrom are provided with respective elongate slots 25, in alinement with each other through which the axle 19 passes. By loosening the nuts 24, 24, the position of the axle 19 may be adjusted in the slots 25, 25 to vary the distance between the sprocket 16 rotatably mounted thereon and the sprocket 17 at the opposite end of the housing 11. A threaded stud member 26 extends transversely to the axle 19 through a leg 23 of the bracket member 21 and has an enlarged attened end in abutment with the axle 19 at a position thereon intermediate the slots 25, 25. The stud member 26 is arranged to prevent movement of the axle 19 toward the sprocket 17 at the opposite end of the housing 11 and its enlarged flattened end serves' as a frictional brake restraining the axle 19 against rotation. It will be understood that the stud member 26 is also adjustable with respect to the axle 19 and the leg 23 of the bracket member 21 through which the stud member 26 extends in order to effect the desired adjustment in the distance between the sprockets 16, 17.

The sprocket 17 at the opposite end of the housing 11 is a positively driven sprocket having an enlarged hub 29, the sprocket 17 being mounted within the housing 11 with its enlarged hub 29 fixedly secured on one end of a rotatable axle or shaft 30 extending outwardly of the housing 11. The rotatable shaft 30 extends transversely to the elongate housing 11 'through a bearing 31 carried by a side wall of the housing 11, the outer end of the rotatable shaft 30 having a pulley 32 xedly secured thereto.

The pulley 32 forms part of a drive means for imparting rotation to the driven sprocket 17, the drive means also including a second pulley 33 of smaller diameter than the pulley 32 and a belt 34 entrained about the pulleys 32, 33. The pulley 33 is xedly secured on the end of a power shaft extending from the housing of a non-reversible electric motor 35. Thus, it will be understood that the belt and pulley drive is operated upon energization of the electric motor 35 to impart rotation to the sprocket 17 for driving the endless chain 15 in a single direction of movement. In this respect, the electric motor 35 and the belt and pulley drive associated therewith provide a remotely controlled source of power for driving the endless chain 15.

In accordance with the present invention, controlled door operator means are provided for transmitting the movement of the chain 15 to the door 10,y the latter means including an upright bracket atixed to the upper end edge of the door 10 at a position intermediate the roller assemblies 12, 12 carried thereby, an operator link or arm 41 pivotally connected to the bracket 40 at one end by a pin 42 and xedly connected at its other end to a link of the endless chain 15 for operably connecting the door 10 with the chain 15, and a circuitbreaker element 43 rigidly mounted on the pivot pin 42 connecting the bracket 40 and the operator link 41 for coaction with a pair of switch mechanisms 44, 45 located on the top wall of the elongated housing 11 at opposite ends thereof. As shown best in FIGURE 5, the bracket 40 extends upwardly into the elongated housing 11 through a longitudinal slot provided in the lower wall thereof, the slot also receiving the roller assemblies 12, 12 to hang the door 10 from the housing 11 in suspended relationship. The bracket 40 is disposed in offset relation to the endless chain 15 with its upper end portion being located at a position substantially intermediate the parallel longitudinally extending upper and lower chain sections. The operator link 41 is L-shaped, comprising a vertically extending base having a laterally extending leg integrally connected to one end thereof. The operator link 41 is pivotally connected at one end to the upper end portion of the bracket 40 by the pin 42, the pin 42 penetrating the end of the vertical base of the operator link 41 remote from the lateral leg thereof. The opposite end of the operator link 41 provided by the lateral leg thereof is iixedly secured to a link in the chain 15 so as to cause the operator link 41, the bracket 40 pivotally connected thereto, and the door 10 to which the bracket 40 -is xedly secured to move with the link in the chain 15 to which the operator link 41 is tixedly secured. It will be observed that the length of the operator link 41 is substantially one-half of the distance between the parallel longitudinally extending upper and lower chain sections and that the axis of the pivot pin 42 connecting the operator link 41 and the bracket 40 is disposed perpendicular to the parallel longitudinally extending upper and lower chain sections and equidistant from the chain sections.

The circuit-breaker element 43 is xedly mounted on the pin 42, being positioned between the bracket 40 and the operator link 41 and rigidly secured to the pin 42. As illustrated in FIGURE 5, an annular spacer washer 46 may be interposed between the circuit-breaker element 43 and the operator link 41 about the pin 42. The circuitbreaker element 43 comprises an upright body portion 56 and a longitudinally extending lateral skirt 51 integrally connected to the upper end of the body portion 50. The skirt 51 includes downwardly inclined opposite end portions 52, 53 and serves as a runway for switch control mechanisms 54, 54 of the switches 44, 45 as will be presently described.

The switches 44, 45 located at opposite ends of the elongated housing 11 are identical, it being noted in FIG- URES 6 and 7 that switch 44 comprises opposed switch contacts contained in a switch housing which is mounted on the top wall of the elongated housing 11 in juxtaposition to an opening 60 formed in the top wall of the housing 11. The switch control mechanism 54 for the switch 44 comprises a lever arm 61 and a roller 62, the lever arm 61 being pivotally mounted at one end within the switch housing and the roller 62 being rotatably mounted on the opposite end of the lever arm 61 which extends outwardly of the switch housing. The switch control mechanism 54 tends to normally assume the position illustrated in FIGURE 7 with the roller 62 protruding through the opening 60 in the top wall of the elongated housing 11 into the interior thereof. When the switch control mechanism 54 assumes the latter position, the opposed switch contacts of the switch 44 are in engagement to close the switch 44. Upon movement of the chain 15 so as to impart appropriate movement to the door operator means, the circuit-breaker element 43 will travel to the position illustrated in FIGURE 6, wherein its lateral skirt 51 is moved across the opening 6G in the top wall of the housing 11 to cause the roller 62 of the switch control mechanism 54 to ascend the inclined end portion 52 of the skirt 51 and to subsequently be elevated onto the main level portion of the skirt 51. As this elevation of the roller 62 occurs, the lever arm 61 is pivoted upwardly about its end within the switch housing to space the switch contacts apart for opening the switch 44. It will be understood that an opening 60 is formed in the top wall of the housing 11 at the opposite end thereof to cooperate with the switch 45 and the switch control mechanism 54 therefor in the same manner previously described in connection with the switch 44 and its switch control mechanism 54. In opening the switch 45, the roller 62 of its switch control mechanism 54 is caused to ascend the inclined end portion 53 of the skirt 51 and to be elevated onto the main level portion of the skirt 51 for pivoting the lever arm 61 of its switch control mechanism 54 to space the switch contacts of switch 45 apart, upon appropriate movement of the circuit-breaker element 43 imparted by movement of the chain 15.

Referring to the wiring diagram of FIGURE 8, it will be observed that the switches 44 and 45 are connected in series in a primary electrical circuit for the motor 35 and are arranged to be alternately opened by the circuit- -chain section.

'5 breaker element 43 when the door 10 has been moved to its fully open or fully closed position for breaking the primary electrical circuit for the motor 35 to stop the operation of the motor 35,;the Switch 44 being opened to stop the motor 35 when the door 10 is moved to open position, and the switch 45 being opened to stop the motor 35 when the door ltis, moved to closed position. ,It will be further noted that the electrical wiring diagram of :FIGURE 8 traces out secondary or starterelectrical cir- `cuits for the motor 35 which include a pair of manually operable switches'70, 71 respectively located on opposite sides of the wall of the building structure having the door opening formed therein. These manual switches 7i), 71 are connected in parallel lwith each other across the serially connected door control switchest44, 45 for establishing separate ,starter electrical circuits through the motor 35 independently of the primary electrical circuit which includes the door control switches 44, 45 in order to supply electric power to the motor 35 upon the closing Vofeither switch 79 or 71 while one of the door control bracket. 4t) with its lateralleg rigidly secured to a link in the chain 15. In this position, the particular chain link to which the operator link 41 isfixedly securedis disposed in the upper-longitudinally extending chain section at an end thereof just prior to executing an arcuate turn in traveling to the lower longitudinally extending chain section. The skirt 51 of the circuit-breaker element 43 engages and elevates the roller 62 of the switch control mechanism 54 of switch A44 to open the switch 44-so that the primary electrical circuit for the motor 35 which includes the switch 44 is broken and the motor 35 is not in operation.

When it is desired to move the door 16 to closed position, either one of the manually operable switches 70 or 71 may be closed by an appropriate manipulation to by-pass or shunt the open switch 44 and complete an alternate secondary or starter electrical circuit for the motor-35 through the manually operable switch 70 or 71 which has been closed. Thus, the motor 35 is energized and operates to drive the chain 15 through the belt and pulley drive imparting rotation to the sprocket 17. -Movement of the chain 15 causes the particular chain link to which the operator link 41 is rigidly connected to travel about an arcuate end path from the upper to the lower longitudinally extending chain section. In so traveling, the chain link causes the operator link 41 to swing in an arcuate path about the pivot pin 42 and to assume a position in which its base portion is brought into overlying relationship with the upper endfportion of the bracket 49 below the pivot pin 42 lwithout causing any vertical adjustment of the door to which the bracket 4t) is rigidly secured (see FIGURE 7). At the same time, the pivot pin 42 reverses its direction of movement intermediate the parallel longitudinally extending upper and lower chain sections, as the chain link to which the operator link 41 is rigidly secured completes its arcuate path of movement Afrom the upper chain section to the lower As the pin 42 moves away from the arcuate endof the chain entrained about the sprocket 17, the circuit-breaker element 43 is carried by the pin 42 and'is moved away from the opening@ in the elongate housing 11 associated with switch 44. ri`he roller 62 of the switch control mechanism 54 for switch 44 is thereby guided along the lateral skirt 51 vof the circuit-breaker .element 43 down its inclined end portion 52. When the circuit-breaker element 43 moves clear of the roller 62, the roller 62 drops further downwardly throughthe unobstructed opening 60 and the lever arm 61 pivots downwardly to close the switch 44.

The manually operable switch 70 or 71 mustbe held in a closed position to continue the operation of the vmotor through the completion of a secondary or Vstarter electrical circuit including thefclosed manually operable switch 7) or 71 for driving-the chain 15 until the circuitbreaker element 43 has traveled suliiciently torelease the roller 62 ofthe switch control mechanism 54 for the switch 44. Once this has been accomplished, the switch 44 will be closed to complete the primary electrical circuit for the motor 35, and themanually operable switch 75 or 71 may be released to resume its normally open position.

The door 1li then continuestotravel to its closed position, being moved by the bracket andthe operator link 41 operably connecting the door 10 with a particular chain link in the traveling chain-15. When `thedoor 10 has been moved to its fully closed position, the circuitbreaker element 43 will have been movedinto engagementfwith the roller 62 ofthe switch control mechanism 54 for switch 45, causing the roller `62 to ascend the inclined end portion 53 of the lateral-skirt 51 and to be elevated onto the main central portion thereof for opening the switch 45. Thus, movement of the-door 10 to its fully closed position opens the switch 45 to break the primary electrical circuit for the motork 35 which includes the door control switches 44, 45, and the operation of the motor 35 is stopped. The door 10 will `then remain in its fully closed position until one of the manually operable switches 7@ or '71 is closed to complete an alternate secondary or starter electrical circuit energizing the motor 35 to drive the chain15 for causing the circuit-breaker element 43 to be moved away -from the switch as the pivot pin 42 reverses direction at the arcuateend of the chain 15 entrainedabout thesprocket 16. The switch 45 is closed in rthe same manner described in connection with the closing of switch 44 when the circuit-breaker element 43-has moved a suicient distance away from Vthe switch 45. The primary electrical circuit for the motor 35 is completed byithe closing of the switch 45, andfthe closed manually operable switch or 71 maybe released to resume its normally open position while the door 10 continues to travel in returning to its fully open position.

The motor 35, as noted,is,preferably a non-reversible type, which is relatively inexpensive las compared to a reversible motor, the non-reversible motor 35 causing the chain 15 to be driven in a single direction for effecting reciprocablemovement ofthe door ,fltlbetween positions opening and closing the door opening in a building structure. When the door 1) changes `its direction of movement, the L-shaped operator link 41 of the door operator means pivots about the pin 42 with respect to the bracket 4t? to compensate for the movement-of the chain link to which the operator link-41 isrigidly secured from one of the longitudinally extending parallel chain sections to the other chain section with the door 10 undergoing no vertical adjustment.

Hfhe component parts of the door operator means in my improved door operating mechanism -are Vcontained within the same elongated housing from which-the door is suspended for sliding movement, Awhere they are shielded `from direct exposure to vforeign matter and are hidden from view. Moreover, my improved door operatingmechanism comprises comparativelyfewcomponent parts of simple character as contrasted tothe cumbersome mechanicalflinkage systems heretofore common in conventional door operating mechanisms and -accomplishes the siiding movement of the door in an eiiicient manner without the necessity of frequent repair.

In the drawings and specification there has been set forth a preferred embodiment of the invention and, although specitic terms are employed, they are-used in a generic and descriptive sense only and not forpurposes of 7 limitation, the scope of the invention being defined in the claims.

I claim:

1. In an apparatus for operating a sliding door,

(a) an elongated housing having a longitudinally extending trackway from which the door is adapted to be hung for movement between open and closed positions,

(b) a pair of sprockets mounted within said housing at opposite ends thereof,

(c) a chain with said housing entrained about each of said sprockets and having first and second substantially parallel chain sections extending between said sprockets,

(d) a non-reversible motor operatively connected to one of said sprockets for rotating said one sprocket in a single direction to drive said chain in a single direction of movement,

(e) a bracket for fixed attachment to the door, said bracket having one end portion extending into said housing and being disposed in a position ofi-set from and substantially intermediate said first and second parallel chain sections,

() an operator link within said housing having an extent substantially one-half of the distance between said first and second chain sections, said operator link being fixedly secured at one end to said chain for movement therewith,

(g) means pivotally connecting the other end of said operator link to said one end portion of said bracket for connecting said chain with the door to impart movement to the door between open and closed positions upon driving said chain in the single direction in response to rotation of said one sprocket by said non-reversible motor,

(h) an electrical motor circuit for energizing said nonreversible motor,

(l) said electrical motor circuit including a pair of serially-wired normally closed switches mounted on said housing at opposite ends thereof, and

(2) pivotal control means associated with each of said switches; each of said pivotal control means comprising (I) a lever arm mounted for pivotal movement about one end operably connected with said switch corresponding thereto and being movable between positions opening and closing its respective switch, and

(II) a roller mounted for rotation on the other end of said lever arm;

() said housing having openings formed therein at its opposite ends for respectively receiving said rollers of said pivotal control means for said switches, and

(j) a circuit-breaker element within said housing carried by said means pivotally connecting said operator link and said bracket, said circuit-breaker element including a skirt alternately movable into juxtaposition with the openings in the housing at its opposite ends to alternately engage and elevate said rollers to pivot the respective lever arm of the roller engaged by said skirt for opening said switch corresponding thereto to break said electrical motor circuit, whereby the operation of said motor stops when the door has been moved to its open or closed position.

2. In an apparatus for operating a sliding door,

(a) an elongated housing having spaced horizontallyextending top and bottom walls and an integral mounting flange extending vertically upwardly from said top wall, said bottom wall of said housing having a slot extending therethrough and longitudinally thereof for substantially its entire length,

((b) a traekway within said housing from which the door is adapted to be hung for movement between open and closed positions, said trackway being mounted upon and extending longitudinally of said bottom wall of said housing adjacent said slot therethrough,

(c) a pair of rotatable sprockets mounted within said housing at opposite ends thereof,

(d) an endless chain within said housing entrained about each of said sprockets and having first and second chain sections extending between said sprockets in substantially parallel relationship to each other and to said walls of said housing,

(e) a non-reversible electric motor carried by said housing adjacent one of said sprockets,

(f) drive means carried by said housing and interconnecting said electric motor and said one sprocket for rotating said one sprocket in a single direction to drive said chain in a single direction of movement when said motor is energized,

(l) said drive means including a iirst pulley carried by and rotatable with the shaft of said motor,

(2) a second pulley operatively connected to and rotatable with said one sprocket, and

(3) a exible drive beit interconnecting said iirst and second pulleys,

(g) a generally vertically-extending door-mounting bracket projecting through and movable longitudinally of said slot of said bottom wall of said housing, said bracket having its upper end portion disposed at all times within said housing in a position off-set and closely-spaced from said first and second parallel chain sections,

(h) an L-shaped operator link having an extent substantially one-half of the distance between said iirst and second chain sections, said operator link being fixedly connected at one end to said endless chain and extending perpendicularly inwardly therefrom for movement therewith,

() pin means pivotally connecting the other end of said operator link to said upper end portion of said bracket for connecting said chain with the door to impart movement to the door between open and closed positions in response to rotation of said one sprocket by said drive means upon energization of said non-reversible motor,

(j) an electrical motor circuit for energizing said nonreversible motor,

(1) said electrical motor circuit including -a pair of serially-wired normally closed switches mounted on said top wall and adjacent opposite ends of said housing, and

(2) pivotal control means associated with each of said switches, each of said pivotal control means comprising (I) a lever arm operably connected with said switch corresponding thereto and being mounted for pivotal movement about one end for movement between positions opening and closing its respective switch, and

(II) a roller mounted for rotation on the other end of said lever arm,

(k) said upper wall of said housing having openings formed therein adjacent said switches for respectively receiving said rollers of said pivotal control means for said switches, and

(l) a circuit-breaker element carried by said pin means pivotally connecting said operator link and said bracket and extending upwardly from said pin means within said housing, said circuit-breaker element including a skirt disposed `adjacent said top wall of said housing and alternatively moveable into juxtaposition with said openings therein to alternately engage and elevate said rollers to pivot the respective lever arm of the roller engaged by said skirt for Sb l@ opening said switch corresponding thereto to break References Cited in the file of this patent said electrical motor circuit, whereby the operation UNITED STATES PATENTS of said motor stops when the door has been moved switch housings mounted upon said top Wall and enclosing said switches.

UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Patent No. 3,172,651 March 9, 1965 Merlin C. Wilson It is hereby certified that error appears in the above numbered patent requiring Correction and that the said Letters Patent should read as corrected below.

Column 7, line ll, for "with" read within Signed and sealed this 3rd day of August 1965.

(SEAL) Attest:

ERNEST W. SWIDER v EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. IN AN APPARATUS FOR OPERATING A SLIDING DOOR, (A) AN ELONGATED HOUSING HAVING A LONGITUDINALLY EXTENDING TRACKWAY FROM WHICH THE DOOR IS ADAPTED TO BE HUNG FOR MOVEMENT BETWEEN OPEN AND CLOSED POSITIONS, (B) A PAIR OF SPROCKETS MOUNTED WITHIN SAID HOUSING AT OPPOSITE ENDS THEREOF, (C) A CHAIN WITH SAID HOUSING ENTRAINED ABOUT EACH OF SAID SPROCKETS AND HAVING FIRST AND SECOND SUBSTANTIALLY PARALLEL CHAIN SECTIONS EXTENDING BETWEEN SAID SPROCKETS, (D) A NON-REVERSIBLE MOTOR OPERATIVELY CONNECTED TO ONE OF SAID SPROCKETS FOR ROTATING SAID ONE SPROCKET IN A SINGLE DIRECTION TO DRIVE SAID CHAIN IN A SINGLE DIRECTION OF MOVEMENT, (E) A BRACKET FOR FIXED ATTACHMENT TO THE DOOR, SAID BRACKET HAVING ONE END PORTION EXTENDING INTO SAID HOUSING AND BEING DISPOSED IN A POSITION OFF-SET FROM AND SUBSTANTIALLY INTERMEDIATE SAID FIRST AND SECOND PARALLEL CHAIN SECTIONS, (F) AN OPERATOR LINK WITHIN SAID HOUSING HAVING AN EXTENT SUBSTANTIALLY ONE-HALF OF THE DISTANCE BETWEEN SAID FIRST AND SECOND CHAIN SECTIONS, SAID OPERATOR LINK BEING FIXEDLY SECURED AT ONE END TO SAID CHAIN FOR MOVEMENT THEREWITH, (G) MEANS PIVOTALLY CONNECTING THE OTHER END OF SAID OPERATOR LINK TO SAID ONE END PORTION OF SAID BRACKET FOR CONNECTING SAID CHAIN WITH THE DOOR TO IMPART MOVEMENT TO THE DOOR BETWEEN OPEN AND CLOSED POSITIONS UPON DRIVING SAID CHAIN IN THE SINGLE DIRECTION IN RESPONSE TO ROTATION OF SAID ONE SPROCKET BY SAID NON-REVERSIBLE MOTOR, (H) AN ELECTRICAL MOTOR CIRCUIT FOR ENERGIZING SAID NONREVERSIBLE MOTOR, (1) SAID ELECTRICAL MOTOR CIRCUIT INCLUDING A PAIR OF SERIALLY-WIRED NORMALLY CLOSED SWITCHES MOUNTED ON SAID HOUSING AT OPPOSITE ENDS THEREOF, AND (2) PIVOTAL CONTROL MEANS ASSOCIATED WITH EACH OF SAID SWITCHES; EACH OF SAID PIVOTAL CONTROL MEANS COMPRISING (I) A LEVER ARM MOUNTED FOR PIVOTAL MOVEMENT ABOUT ONE END OPERABLY CONNECTED WITH SAID SWITCH CORRESPONDING THERETO AND BEING MOVABLE BETWEEN POSITIONS OPENING AND CLOSING ITS RESPECTIVE SWITCH, AND (II) A ROLLER MOUNTED FOR ROTATION ON THE OTHER END OF SAID LEVER ARM; (I) SAID HOUSING HAVING OPENINGS FORMED THEREIN AT ITS OPPOSITE ENDS FOR RESPECTIVELY RECEIVING SAID ROLLERS OF SAID PIVOTAL CONTROL MEANS FOR SAID SWITCHES, AND (J) A CIRCUIT-BREAKER ELEMENT WITHIN SAID HOUSING CARRIED BY SAID MEANS PIVOTALLY CONNECTING SAID OPERATOR LINK AND SAID BRACKET, SAID CIRCUIT-BREAKER ELEMENT INCLUDING A SKIRT ALTERNATELY MOVABLE INTO JUXTAPOSITION WITH THE OPENINGS IN THE HOUSING AT ITS OPPOSITE ENDS TO ALTERNATELY ENGAGE AND ELEVATE SAID ROLLERS TO PIVOT THE RESPECTIVE LEVER ARM OF THE ROLLER ENGAGED BY SAID SKIRT FOR OPENING SAID SWITCH CORRESPONDING THERETO TO BREAK SAID ELECTRICAL MOTOR CIRCUIT, WHEREBY THE OPERATION OF SAID MOTOR STOPS WHEN THE DOOR HAS BEEN MOVED TO ITS OPEN OR CLOSED POSITION. 